Mopeka Pro Check Water Sensor

Interesting, guess I am lucky, factory tank indicators are pretty accurate.  However, I clean black tank for 10 minutes using built in tank flush and finish using gate valve flush as well.  Gray gets aggressively cleaned 6 times a year.   I switched to this tank treatment years ago, this is the best! Double dose on cleaning day let it sit for several hours, clean as a whistle.

https://amzn.to/4aNlTKT

@shadow, I should have mentioned, or you'd find out reading the manufacturer's info, this isn't for black tank use. Mopeka recommends this sensor for fresh or grey water only. Too many solids absorb too much of the signal so the accuracy can't be confirmed.

As far as accurate, I'd prefer to know more than "you might be on your last 15 gallons of fresh water". Those light divisions of 1/3 are nearly worthless for fresh water boondocking inventory. Gray is intuitively linked to fresh water usage and black is easy to see how much room is left - just look down the hole!

Nice write up Dave.

I've considered both the Mopeka sensor for FW and also the Garnet, Sealevel sensor system that provides info on all the tanks  So, far, I haven't pulled the trigger.

Our FW stock monitor is fairly accurate, but as you mentioned, only down to the 1/3 level.  Our GW tank gives us a warning when the shower drain starts makes noise or starts spilling out into the shower.

Our BW tank gives me the most concern.  I can't look down the hole to see the water level, as there is a bend in the plumbing. 

If, and/or when, you buy that shinny new 855s TC, you will be stopping to dump much more often than in your TT. 

@Les1 posted:

Nice write up Dave.

I've considered both the Mopeka sensor for FW and also the Garnet, Sealevel sensor system that provides info on all the tanks  So, far, I haven't pulled the trigger.

Our FW stock monitor is fairly accurate, but as you mentioned, only down to the 1/3 level.  Our GW tank gives us a warning when the shower drain starts makes noise or starts spilling out into the shower.

Our BW tank gives me the most concern.  I can't look down the hole to see the water level, as there is a bend in the plumbing.

If, and/or when, you buy that shinny new 855s TC, you will be stopping to dump much more often than in your TT. 

Indeed ... the dark chalange! 😅

@VigII posted:

Tools were minimal. To cut the circle in the tank tub to mount the boat hatch in, one could use a utility knife but I used a zip tool in my Dremel tool. Just be careful to go only as deep as the tub is thick. I chose a place near the dip tube from the pump above.  Push upward to asses the flexation of the tub to be sure nothing is between the tank and tub. Clean up the circle with the knife. I cut shallow enough that I had to cut the insulation with the knife only enough to fold it to the side. Follow the Mopeka instruction and install the sensor trying to choose a place that is as close to perpendicular to the top of the tank as possible, you won't know until the hole is open.

Finish up by installing the boat hatch. Make sure the screws are only long enough to just clear the tub thickness. I ground off the points on the sheet metal screws to be sure they couldn't puncture the fresh tank.

Dave, how about a photo or two for a better idea of the hatch portion of your install.

I knew I wasn't going to get away without more pics! 😅 I'll post a few tomorrow ...

@Brubie posted:

Dave, how about a photo or two for a better idea of the hatch portion of your install.

Here they are ...

Fresh water tank enclosure with desert patina ...

I located the port about 13+" in from curbside ...

... and about 9" back from the rear.

The opened port.

Insulation pulled back to see the sensor and lurking PVC pipe.

Thanks for posting those images, Dave, it makes your installation much clearer. Couple questions:

1) When installing the hatch, did you use the plastic epoxy suggested in the video?

2) Were you just lucky missing the "lurking PVC pipe" or could that be a problem when choosing the hatch location?

@Brubie posted:

Thanks for posting those images, Dave, it makes your installation much clearer. Couple questions:

1) When installing the hatch, did you use the plastic epoxy suggested in the video?

2) Were you just lucky missing the "lurking PVC pipe" or could that be a problem when choosing the hatch location?

1) I used butyl tape and shortened SS screws. Love the butyl stuff because  it's sticky as all get-out and never dries. One can remove the piece with some determination where with epoxy it's going to stay there.

2) That was actually a little of both! I pushed up on the tub to find a soft flex area big enough for the port. After I drew the porthole in white pencil, I pressed around the drawn hole's perimeter to be sure there was flex. A few inches toward where I discovered the lurking pipe, there was no flex. I felt good about plunging forward and no ill effects occurred. Was it luck or planning?

Based on the quality of your past posts, I'm betting it was planning over luck. Thanks for posting this and the extra details about the butyl tape. I've got a water sensor and hatch on order.

@VigII posted:

The next step after the bubble level is to enter the depth of the tank. I didn't worry about that because the reading will only accurately reflect the gallonage if the volume is known. I used the hose end meter I always used. I filled the empty tank with 11.25 gallons of water. 11.25 gallons equates to 25% of the 45 gallon tank. I varied the tank depth inches until the Mopeka Pro read 25%. I proceeded to 15 gallons representing the old light set of 1/3 of a tank and the Mopeka Pro read 33%. I was very happy to see this level of accuracy. It's been that way so far each time I've filled the tank to various levels.

I like this idea. Nicely done.  This is probably now on my list.

One more thing you may want to try out in the calibrating step... I noticed, when I was calibrating my "sight-glass" mod, is that my tank had several unusable gallons at the bottom.  Three I think.  I don't know if that is a normal condition or not.  I figured that out, when after draining the tank completely and de-priming the water pump, the pump would not re-prime until there were 3 gallons in the tank.  I did not test the other direction ... in other words, if the pump was still primed, would it pick up the last three gallons?  In your set up, it might be an easy thing to test ... when Mopika says there are only 5 gallons left, turn on the pump and see if how many it says are left when the water stops flowing.  Just a though.

Side note:  The "sight-glass" still works and is way better than the indicator light for that bottom 1/3rd.  But, it isn't very good when you get down to the last 5ish gallons... and it is kind of a PITA to keep clean.  I think I may give Mopika a try.

@_Steve posted:

I like this idea. Nicely done.  This is probably now on my list.

One more thing you may want to try out in the calibrating step... I noticed, when I was calibrating my "sight-glass" mod, is that my tank had several unusable gallons at the bottom.  Three I think.  I don't know if that is a normal condition or not.  I figured that out, when after draining the tank completely and de-priming the water pump, the pump would not re-prime until there were 3 gallons in the tank.  I did not test the other direction ... in other words, if the pump was still primed, would it pick up the last three gallons?  In your set up, it might be an easy thing to test ... when Mopika says there are only 5 gallons left, turn on the pump and see if how many it says are left when the water stops flowing.  Just a though.

Side note:  The "sight-glass" still works and is way better than the indicator light for that bottom 1/3rd.  But, it isn't very good when you get down to the last 5ish gallons... and it is kind of a PITA to keep clean.  I think I may give Mopika a try.

I was very tempted to do your sight glass mod. I never moved on it because I had a pretty good 'windage' guesstimate by knowing how many gallons I started out with. Then I saw the Mopeka water tank gizmo!

The gauge doesn't seem to be able to gauge the last ~5 gallons in the tank. It re with poor quality signal.  Perhaps that is because I have it mounted on what appeared to me to be a slope in the tank near the water pickup. Maybe that's where the hidden 3 gallons you describe is, in that little well.

I'm not certain there is a well/low spot there. The slope makes me think there is at least in my tanks installation. In all the assembly line pictures I've seen it looks like the tanks are uniform. Perhaps that PVC pipe running towards the drain pushes up on the bottom of the tank physically slightly deforming it and forming the well as a result.

@VigII posted:

I'm not certain there is a well/low spot there. The slope makes me think there is at least in my tanks installation. In all the assembly line pictures I've seen it looks like the tanks are uniform. Perhaps that PVC pipe running towards the drain pushes up on the bottom of the tank physically slightly deforming it and forming the well as a result.

Having now done the job and knowing what you know now, if you had a "do-over" would you locate in the same place?  Or would say "move it over this or that way a few inches."?

The picture looks as though the 6 inch port was an appropriate size choice.  In the "do-over", would you pick that same size again?

Cheers

@_Steve posted:

Having now done the job and knowing what you know now, if you had a "do-over" would you locate in the same place?  Or would say "move it over this or that way a few inches."?

The picture looks as though the 6 inch port was an appropriate size choice.  In the "do-over", would you pick that same size again?

Cheers

Port size is fine at 6" diameter.  As for placing the hole for the port I'd stay the same distance from the back of the tub and move the centerline an inch to the curb side. Remember these are crew built units so use my placement with your own assessments. You should find the proper tub flex to locate the right spot but at least you have a general area with what I measured - YMMV!

I've since added a sensor on my freshwater tank per @VigII installation posted here. Easy to install. I was a little worried about the six inch port hatch vibrating loose (as things do when traveling) so added a small strip of duct tape just to make sure the screw-on hatch top doesn't end up along the roadside. So nice now to have a more accurate freshwater monitor! Thanks, Dave, for your good writeup.

@Brubie, I'm glad it helped & you are welcome.

Somehow, I missed this post when it was first posted.  It's nice to have a solution that doesn't require drilling into the tank.  I really like this idea.  It's now on my to do list.

@Brubie posted:

I've since added a sensor on my freshwater tank per @VigII installation posted here. Easy to install. I was a little worried about the six inch port hatch vibrating loose (as things do when traveling) so added a small strip of duct tape just to make sure the screw-on hatch top doesn't end up along the roadside. So nice now to have a more accurate freshwater monitor! Thanks, Dave, for your good writeup.

@Brubie, I just received my sensor and hatch today.  Since we both have 2018 model year 1995's, I'm wondering what you can share about the location you chose for the hatch, anything else you may have learned and, of course, any photos you may be able to share.

-Thanks

@PeterPam posted:

@Brubie, I just received my sensor and hatch today.  Since we both have 2018 model year 1995's, I'm wondering what you can share about the location you chose for the hatch, anything else you may have learned and, of course, any photos you may be able to share.

-Thanks

I followed Dave's installation instructions, including his precise measurements which I found to be the same for my trailer. I've had no issues with the unit since installing it and it continues to work well. I may add another sensor to my gray tank next summer.